Research and Conservation

Mules and horses navigated the steep trails of the Sierra Nevada for early Euro-American explorers, supported the US Army's efforts to subdue the American Indians, and carried miners' supplies into the mountains. Ranchers hired packers when they moved their cattle to graze in the Cascade Valley and along the Middle Fork San Joaquin, and government agencies hired them to repair roads, build fire lookouts, stock trout into streams and creeks, and shuttle supplies for backcountry geologic surveys.

Eventually it was tourists who provided the primary clientele for Sierra Packers. Pack trips enabled people to cover long distances and experience the backcountry in relative comfort, gaining popularity in the first half of the 1900s. The Sierra Club had annual month-long pack trips with 100 mules for their 200 participants, but as use grew, so did concerns about the environmental impacts of packing.

Starting in the 1920s, the US Forest Service and National Park Service were regulating the use of pack stock in the backcountry, and in 1936 wildlife technician E. Lowell Sumner warned that "unless active protection measures are taken now, the chance that these meadows will recover completely is slight." In 1941 a Sierra Club committee began providing instructions and maps for packers, and limiting the use of certain fragile areas. These were accepted and followed by some, while others continued to bring large parties to scenic spots and leave behind trash, fire pits, shelters, and trampled vegetation. The High Sierra Packers Association drew up a "packer's code" in 1948 in order to help preserve the wilderness character of the land, on which they relied so heavily.

The wilderness character of the landscape was a resource that the packers' livelihoods depended on, and many members opposed plans for a trans-Sierra highway. Throughout the Ansel Adams Wilderness designation from the late 1950s to 1984, a coalition of local packers, business owners, and conservationists secured an important victory when they persuaded then-governor Ronald Reagan to halt a proposed trans-Sierra highway.

Today, the packing tradition continues at both commercial pack stations in the Sierra and with federal agencies. The National Forest Service and the National Park Service both rely on pack stock to supply back-country camps and trail crews, to complete trail work in wilderness, and to pack in employees and supplies. The Inyo National Forest is home to one of the US Forest Service's Pack Stock Centers for Excellence, which teaches traditional wilderness pack skills and serves as a valuable resource for forests throughout the west. National parks in the Sierra including Devils Postpile rely on pack stock and Park Service packers to assist with trail work, rescues, and other needs in remote locations. See our current stock regulations for recreational use of stock in the monument.


Despite benefiting from the rapid industrialization of the late 1800s, many Americans worried about diminishing natural resources and the effects of urban life on their physical and intellectual well-being. As tourists they often wanted to seek out the last vestiges of the wilderness that many believed had been the origin of the American character.

The Devils Postpile area came under federal protection in 1890 when it was included within the boundaries of Yosemite National Park. Two years later John Muir organized the Sierra Club with a group of professors and businessmen who hoped to build a constituency for preservation by blazing trails through the Sierra backcountry for invigorating recreation. Muir believed that "if people in general could be got into the woods, even for once, to hear the trees speak for themselves, all difficulties in the way of forest preservation would vanish."

In 1905, however, mining, timber, and grazing interests succeeded in having the Devils Postpile area transferred from Yosemite to the newly designated Sierra National Forest, which meant that the US Forest Service could open it to commercial development. In 1910, District Engineer Walter Huber received an application to blast portions of the Postpile formation to build a dam. Arguing that its scenic and scientific value outweighed the economic benefits of a dam in the area, Huber convinced Forest Service officials and President William Taft to join the Sierra Club in supporting the establishment of a national monument at the Postpile.

In 1930, guide Mon Griggs set off on the John Muir Trail with novice packer Norman "Ike" Livermore Jr. and four clients. On the fifth night, they camped west of the Minaret divide at a raucous gathering point for sheepherders and cattlemen. Griggs promised that on the next night they would be "in the most beautiful camp in the whole mountains." When they arrived at Pumice Flat, however, they were surprised to find a valley full of automobiles. Griggs had not known of the construction of the Minaret Summit mining road.

Later, when Livermore was on the Sierra Club board and then Governor Ronald Reagan's secretary of resources, that experience spurred him to oppose the extension of roads into the High Sierra backcountry. For Livermore, the Middle Fork Valley represented an idyllic wilderness better left undeveloped and accessible only to those willing to pack in by foot or stock. The plan to develop a trans-Sierra highway in 1972 would have greatly increased tourism, but also threatened the rustic and wilderness quality of the area, so a coalition of packers, tourism business owners, and local conservationists defeated the plan. Their efforts continued into the 1980s and were successful in 1984 in connecting two Forest Service "primitive areas" with the Ansel Adams Wilderness which includes three-quarters of the monument and forever prevents any development within the area.


When Devils Postpile National Monument was established in 1911, little was known about the geologic processes that had shaped the Postpile formation and its surrounding landscape. For most observers through the early 1900s, the Postpile was notable primarily for its strange appearance and scenic setting.

US Geological Survey topographer François Matthes produced the first authoritative survey of the Postpile and the surrounding area in 1930 as part of a larger project to document the geologic history of Yosemite and the High Sierra. He also published short articles for the Sierra Club Bulletin on aspects of Sierra geology. His 1930 essay on Devils Postpile and the surrounding region brought attention to a little-known area and became the basis for subsequent geologic studies of the Mammoth volcanic complex.

Unlike most previous observers who viewed the Postpile formation as a geologic oddity, Matthes described it as the most visible example of the volcanic and glacial processes that shaped the Sierra crest in the Mammoth region. Matthes conducted the first detailed study of the origins of the Postpile, in which he concluded that the basaltic lava of the Postpile had erupted from Mammoth Pass from 100,000 to 200,000 years ago, between two of the Sierra's major glacial epochs (later found to be incorrect). Matthes also described the action of the Middle Fork San Joaquin Glacier, which carved away all but the most resistant portions of the basalt obstruction.

Although appearing as "a mere hummock in landscape dominated by mile-high peaks," Matthes wrote, "the columns that form its steep west front, facing the river, are exceptionally high, straight and clean cut;those at its southern end are remarkable for their curvature and their radial arrangement with respect to a center at the top of the pile. Strikingly beautiful, also, are the six-sided or five-sided end facets of the columns which in places still gleam with the polish that was imparted to them by the overriding glacier."

The next significant geologic work at the monument took place following its transfer to the National Park Service in 1934, when Yosemite managers sent Theodore Cronyn to survey themonument and catalog its resources. Cronyn documented several other features of geologic interest, including the basalt columns of the Buttresses, the prominent cliff across the river and downstream from the Postpile, and several large, egg-shaped glacial erratics that had been deposited as the Middle Fork glacier retreated.

Budget cuts during World War II prompted a debate about whether Devils Postpile deserved national monument designation based on its significance as a scientific resource. After inspecting the area in 1951, Park Service Naturalist Dorr Yeager concluded that the Postpile formation was "unique among geologic phenomena of this country" and that Rainbow Falls, although not as spectacular as the falls in the Yosemite Valley, was beautiful and should be retained in the monument.

In a 1952 article for Yosemite Nature Notes, Ranger Naturalist Richard Hartesveldt synthesized what was known about the geology of the Postpile area and described the ongoing processes of geologic change evident in the Middle Fork Valley. In 1963, Ranger naturalists Keith Trexler and William Jones revised and updated the article, republishing it as a tourist brochure titled Your Guide to Devils Postpile National Monument.

In the 1980s, park managers revised the monument's geologic story, estimating the age of the lava at approximately 100,000 years and identifying its source as a collection of vents near thepresent-day Pumice Flat campground. In recent years, the Park Service has worked with the USGS to pursue more in-depth studies of the Postpile lava and other volcanic features of the monument and the surrounding area. In 2010, USGS scientist Wes Hildreth evaluated samples of the Postpile lava using the newer dating process that established a more precise age of approximately 82,000 years.

Last updated: September 22, 2015

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